Manufacture of detonating fuse



Aug. 22, 1933.

W. O. SNELLING ET AL I v iANUFACTURE 0F DETONATING FUSE Filed.July 28, 1932 0 v: H S m D B B DENSITY I WA LTEF? 0.. SNELL 1 NG CLARENCE 13. Hoe/1 INVENTORS 'v BY M LQ.,L|IATTORNEY UNITED STATES PATENT OFFICE MANUFACTURE OF DETONATING FUSE Walter 0. Smelling and Clarence B. Koch, Allentown, Pa, assignors to Trojan Powder Company, a Corporation of New York Application July 28, 1932. Serial No. 625,340

' 4 Claims. (Cl. 102-42 Our invention relates to improvements in the be avoided to a considerable extent, and it has manufacture of detonating fuse, and more paralso been discovered that the admixture of a ticularly relates to the preparation of detonating more sensitive detonating agent than trinitrofuse of improved ability to withstand long contoluene with the trinitrotoluene used as the prin- 5 tinued storage without loss of sensitiveness. The cipal detoneting h r n cordeau also results in 60 principal object of our invention is to provide p ove keeping properties ability to Withmeans for the manufacture of detonating fuse stand storage without excessive loss of sensitiveor cordeau of initial high sensitiveness, and ness, as has been pointed out in U. S. Patent which maintains this initial high sensitiveness 1,241,705 of June 1, 1920 to Cope.

without substantial diminution with time. We have discovered means by which detonating 65 Detonatlng fuse or cordeau consists of an outer fuse or cordeau of improved sensitiveness can be tube or sheath of tin, lead, or any other suitable produced in an e t emely Simple a inexpensive metal or alloy, and an inner core or member of way, and the cordeau produced by our new method trinitrotoluene, trinitrobenzene, tetryl, pentaerypossesses x pti nal abili y to wi hstan l n thrite tetranitrate or any other suitable detonacontinued storage Without reduction in sensitive- 70 ing agent or mixture of detonating agents. Deness with time. tonating fuse is made byfilling the outer sheath In order to explain the novel features involved or tube with a molten charge of the fused dein our present invention we will now point out tonating agent, permitting this fused charge to certain relationships which exist in cordeau made solidify, and then increasing the length and deby the methods at present known, in order to 75 creasing the diameter of the composite tube by distinguish these relationships from the correa series of rolling or drawing operations as despo relationships existing in cordeau ade scribed in U. S. Patent 869,219 of October 22, by our present invention. In the manufacture 1907 to Lheure or U. S. Patent 882,154 of March of cordeau by the methods known up to this time,

17, 1908 to Lheure, or by increasing the length and a metal tube is filled with a molten detonating g0 decreasing the diameter of the composite tube agent, and is then increased in length and deby a swaging operation, as described in U. S. c d n diameter y a series of rolling, w- Patent 1,741,380 of December 31, 1929 to Snelling n r w in p r i n until cordeau of the and Koch, desired final diameter is secured. It is imperative It has been found t t detonating fuse or that the tube should be completely filled with the 5 cordeau made by either of the methods known moltenfietonating agent, since any large bllbup to this time has satisfactory sensitiveness at ble mterruption in the Pxplosive core will 0f the time of its manufacture, when made with courselfmgthen materially K rolllnsdrewms trinitrotoluene or other detonating agent of high or swaging w t and prevent the sausfactory functioning of the finished fuse, through 90 purity, but with age this initial high sensitivebTt f th 1 1 k at f dually decreases so that detonating fuse ma 1 I y 9 6 re a 8 onaflmg one ness gm of the thin core of tnmtrotoluene to ump any or cordeau several years after its manufacture gap or open Space in the column of explosive often shows insufficient sensitiveness to enable material.

40 the detonating Wave to Propagate complgtely Accordingly, in all cordeau which has been 95 through the material, and failure to detonate made up t t t of t invention, there h pa junctions and Connections of trunk lines been a direct and necessary relationship between with subsidiary lines of cordeau are of frequent th i itial dia t of th rd th final d1 occurrence. ameter of the cordeau, and the density of the vDiscovery of the fact that detonating fuse or contained charge of trinitrotoluene or other det- 100 cordeau which has been stored for some time onating agent used. The initial tube, before beshows reduced sensitiveness is not new, but on ing drawn down or swaged down to its final diamthe contrary has been recognized for many years eter, is filled with the molten detonating agent as being one of the outstanding disadvantages which solidifies within the tube to form the-solid of an otherwise excellent means of simultaneousdetonating agent at its normal density when 105 1y transmitting'detonation to a number of sepasolidified from fused condition. The operations rating charges of high explosives. It has been of drawing or swaging the filled tube, to decrease discovered that by the use of refined trinitroits diameter and increase its length, breaks up toluene of exceptional purity the tendency tothe fused detonating charge and reduces it to ward reduction of sensitiveness with time can pulverulent condition, with the production of a 11 highly compressed pulverulent mass within the lead tube, the exact density of this pulverulent mass being determined by the volume and pressure relationships existing during the drawing and swaging operations. For example, when lead tube 16 mm. inside diameter and 19.5 mm. outside diameter is filled with molten trinitrotoluene of. high purity, and this trinitrotoluene is then allowed to cool and solidify, the density of the fused trinitrotoluene within the tube is initially about 1.60. Upon drawing this initial tube down to a final outer diameter of 6 mm., corresponding to an inner diameter of 4.25 mm. and a wall thickness of 0.875 mm., the pulverulent charge of trinitrotoluene within the finished cordeau has a density of approximately 1.30, and it is interesting to note that up to the time of the present invention no method was known of modifying this density, since the density of the main charge of pulverulent trinitrotoluene was a definite and necessary factor of the drawing or swaging operation used in manufacturing the detonating fuse or cordeau. According to the initial diameter of the lead tube and the final diameter of the finished cordeau, the charging density of the pulverulent trinitrotoluene in ordinary commercial cordeau having an outer diameter of 6 mm. shows a normal variation in cordeau made by the drawing operation of from 1.20 to 1.30, and shows a normal variation in cordeau made by the swaging operation of from 1.30 to 1.40, the density of the pulverulent charge of trinitrotoluene in cordeau made by the swaging operation being somewhat greater than the density of the charge in cordeau made by the drawing operation, because of the greater pressure applied to the trinitrotoluene core in the swaging operation, as compared with the corresponding pressure produced in the drawing operation.

' Ithas long been known that the sensitiveness to detonation of many explosives is materially influenced by the density of the material, and some explosives are well known to become highly insensitive when subjected to high pressure. Up to the time of the present invention, however, the density of the pulverulent charge of trinitrotoluene in cordeau has never been considered to have significance, in view of the fact that whether cordeau is made by the drawing process or by the swaging process it shows satisfactory initial sensitiveness, and shows no indications whatever of being excessively compressed or of being charged to so high a density as to interfere with the normal progress of the detonating wave.

We have discovered, however, that although the initial sensitiveness of pulverulent trinitrotoluene is not measurably influenced by the density of the pulverulent material, this is not true of the sensitiveness after storage for any considerable length of time. Apparently, the closeness of contact of the pulverulent particles determines the degree to which recrystallization of the material occurs, the finely divided pulverulent particles ultimately agglomerating or consolidating, and partially recrystallizing or reforming into particles of larger crystal size, with very serious reduction in sensitiveness, and the reduction in sensitiveness being materially greater in the case of trinitrotoluene of a melting point under C. than it is with trinitrotoluene having a melting point higher than this figure, desensitization with time being determined by the percentage of impurity present in the detonating charge, and being materially greater in the case of slightly impure trinitrotoluene than it is in the case of trinitrotoluene of high purity.

Our studies of the effect of time on the sensitiveness of cordeau indicated the desirability of modifying the density of the inner core of cordeau independently of the reduction which is determined by the operations of drawing down or swaging down the original tube to the desired final dimensions, but all efforts to introduce light porous-filling materials, air bubbles, foam or the like as a means of reducing the density of the core proved unsuccessful, and all known methods of drawing, rolling and swaging the outer tube were found to produce definite correlated densities in the inner core of explosive material.

We have now discovered a method by which we can modify the density of the inner core of explosive material independently of the degree of reduction or "drawing down of the outer tube or casing, and our method is capable of controllably modifying the density of the inner core of explosive material over a satisfactorily wide range to enable us to obtain cordeau of longer effective life without decreasing sensitiveness than can be obtained by any of the methods previously known.

In the simplest form of our invention we first distort a tube by a preliminary rolling or pressing operation so that this tube is no longer circular in cross-section. Although we prefer to distort the tube so that after distortion it is elliptical in cross-section, it will of course be evident that a circle forms the figure which has maximum area for any given periphery, and. that accordingly any uniform deviation from a circle will produce a figure in which the relationship between the cross-sectional area and periphery will be reduced, as compared to the relationship which exists in a circular tube. We prefer to distort our metal tubing to form an ellipse in which the major diameter is between 1 and 3% times the minor diameter, and we next fill this tube with molten trinitrotoluene while it is in such uniformly distorted condition along its entire length. The molten TNT is permitted to harden in the usual way while the tube is in its distorted condition, and the distorted tube containing its solidified core of trinitrotoluene or other explosive agent is then subjected to a rolling or pressing operation to restore it to circular form. Upon being so restored to circular form the outer tube or casing possesses substantially the circumference of the original tube, but the amount of contained trinitrotoluene corresponds only to the reduced cross-sectional area of the ellipse which existed at the time the tube was filled with the molten detonating material, and accordingly the density of the contained trinitrotoluene is correspondingly reduced. Upon now subjecting the tube with its contained core of explosive material to rolling, drawing, or swaging operations to reduce its diameter to the diameter desired in the final cordeau there occurs a tendency to constantly approach the usual ratio of the diameter to the density met with in ordinary cordeau, although this ratio is never quite reached, owing to the initial advantage obtained as a result of the reduced filling density obtained as a result of the novel filling method as herein described. The larger the initial diameter of the lead tube, and the less the distance between the foci of the ellipse, the higher will be the final density of the explosive core in the finished cordeau, and accordingly by suitable control of the diameter of the O ginal lead tube, and suitable distortion of us cordeau which resists storage for many months, at temperatures corresponding to the maximum summer temperatures met with in storage magazines, without any perceptive reduction in sensitiveness occurring.

Inthe drawing forming part of this application Figure 1 is a cross-sectionalview of a lead tube filled with trinitrotoluene in accordance with the usual procedure followed in the manufacture of cordeau. Figure 2 is a cross-section of a lead tube filled with trinitrotoluene in accordance with the procedure which we have-discovered. Figure 3 is a cross-section of the tube shown in Figure I 2, after this tubinghas been restored to circular outline. In all of the figures, A is the outer tubing of lead, tin or other metal. In all of the figures B is the core of trinitrotoluene or other explosive mixture. i

The material of which. the outer tube'or casing is made does not form any part of our present invention, and although we prefer to employ lead as the material from which the outer tube or casing is made, it will be evident that other metals, and particularly other ductile metals such as tin and copper, or alloys of lead and tin, lead and antimony, or lead, tin, and antimony may be used with equal success. We may also employ, in cases where such procedure may be desirable, a composite tube formed with an outer layer of a metal such as lead and an inner member of tin or other metal, such composite tube having advantages in cases where the explosive material has any tendency to react with the metal forming the body of the outer tube or casing. As our explosive core we prefer to employ trinitrotoluene, but we may employ any other suitable detonating agent such as picric acid, tetryl, or the like.

We are of course aware that in the manufacture of cordeau prior to our invention it is quite possible, and indeed is most likely, that some portions of the lead tube may have accidentally become distorted in form through injury in handling, and that notwithstanding the careful inspection which is usually given to the tubing before being filled with trinitrotoluene, it is quite likely that at times tubing which has been locally thus injured and distorted at one or more points along its length may have been filled with trinitrotoluene and may have been manufactured in finished cordeau. In view of the possibility just stated, we wish to expressly disclaim as any part of our invention the manufacture of cordeau from tubing which has been subjected to such accidental injury, and we wish to state that our invention is to be considered as limited to the process which comprises the uniform distortion of tubing along substantially its entire length before being filled, and the uniform filling of such distorted tubing to form a non-circular tube having substantially the same cross-section at all points along its length, and possessing at all points along its length a cross-sectional area greater than the area of a circle corresponding to the normal diameter of the lead tubing used.

During our investigation of the manufacture of cordeau by the method herein described we have discovered an important advantage of our present method of manufacture which we did not know at the time that we began our work, but which became evident in the course of our investigation of cordeau made by our present process.

We have'discovered that the "tendency of'the outer tubing to break or fracture during manufacture or as a result of fiexure during or after manufacture is greatly reduced in cordeau made by our present process as compared with cordeau made by the processes in use up tothe time of our present invention. Although at first we could find no reason to explain the greater strength of the outer casing of cordeauwhen made by our present invention, as compared with cordeau as made by the methods earlier known, we have now found that during the solidification of trinitrotoluene or other crystalline detonating agent within the tube used in the manufacture of cordeau the crystals which form are somewhat harder than the boundaries between these crystals, and that when the filled tube is subjected to operations to decrease its diameter and increase its length. the effect of the pressure applied to the tube is to cause the crystalline mass to form indentations on the inner wall of the tubing propcrtional to the hardness of the individual crystal particles at such points, so that tubing after initial treatment when subjected to heat to remove the inner core shows a noticeably roughened surface. Upon being subjected to further treatment to increase its length and decrease its diameter, these initial roughnesses form the source of differ ences of thicknesses in the wall of the finished cordeau, and owing to the great increase in length and decrease in diameter which occurs in the drawing operation, even a furrow or indentation of very minor depth becomes a source of conture of the distortion of the tube permits of relief to the shearing forces applied to the crystals due to the distortion of the tube producing simultaneously modified and increased cross-sectional area available for expansion of the material. As a result of this condition, which we discovered accidentally during the course of our work, we are able to produce by our present process of manufacture not only cordeau of materially improved sensitiveness, but also cordeau which possesses a notably stronger outer metal wall than is produced by other methods of manufacture, and we have found that the tendency of the lead wall of our cordeau to pierce or break or fracture during manufacture or subsequent to manufacture when subjected to bending or other action is notably reduced as compared with cordeau made bythe process of manufacture known and practiced up to the time of our present invention.

Although we prefer to use ordinary lead pipe or tubing as our raw material, and to distort this lead tubing to elliptical or non-circular crosstice of our present invention, we wish to call particular attention to the fact that it is quite possible to avoid this initial distorting step by the original producion of non-circular tubing by the extrusion of lead from a press provided with elliptical or other non-circular dies. The significant part of our invention is the filling of a noncircular tube with a molten detonating agent and be made within the limits of the disclosure as herein made, and accordingly no limitation of our invention should be made except as indicated in the appended claims.

We claim: 1. In the manufacture of detonating fuse the process which comprises filling a metal tube of non-circular cross-section throughout its efiective length with a molten detonating agent, per-' mittin'g the detonating agent to solidify while the tube remains non-circular in cross-section, distorting the tube to circular cross-section and decreasing the diameter and increasing the length of the filled tube to form cordeau therefrom.

2. In the manufacture of detonating fuse the process which comprises filling a. metal tube of elliptical cross-section throughout its effective length with a molten detonating agent, cooling to solidify the detonating agent and thereafter ap plying pressure to the elliptical tube in the direction of its major axis to distort the tube to circular cross-section and thereafter decreasing the diameterand increasing-the length of the filled tube to form cordeau therefrom.

3. In the manufacture of detonating fuse the process which comprises distorting a metal tube of circular cross-section to form tubing which is of non-circular cross-section uniformly over its effective length, filling the tube witha molten detonating agent, and permitting this molten detonating agent to solidify while the tube is of non-circular cross-section and thereafter restoring the filled tube to circular form and decreasing its diameter and increasing its length to form cordeau therefrom.

4. In the manufacture of detonating fuse the process which comprises charging a molten detonating agent into a metal tube the cross-sectional area of which is uniformly less than the crosssectional area of a circle having a-circumference equal to the perimeter of the tube, permitting the molten detonating agent to solidify, distorting the tube to circular cross-section and thereafter decreasing the diameter and increasing the length of the filled tube to form cordeau therefrom.

WALTER O. SNELLING. CLARENCE B. KOCH. 

